The massive sewage pipe that ruptured and leaked millions of gallons of raw waste into the Potomac River has returned to operation after the completion of emergency repairs. The utility that runs Washington’s water and sewage systems reported Saturday that it had completed testing to determine whether the 72-inch diameter pipe could handle the flow. The pipe broke on Jan. 19 and spilled about 250 million gallons over five days. DC Water worked with the Environmental Protection Agency and other agencies to repair the leak and monitor the ecological impact on the river. Other work on the pipe and system could take months.